Scrap polyethylene terephthalate (PET) and PET production waste are often landfilled. Landfilling of these materials represents, among other things, a loss of raw material, and a potential ecological problem, if improperly landfilled. Accordingly, an economical process for the recycling of these materials is desirable.
The recycling of scrap PET and PET production waste, in general, is known. The materials can be reacted with methanol, i e., "methanolysis", to produce dimethyl terephthalate (DMT) For example, see U.S. Pat. Nos. 2,884,443; 3,037,050; 3,148,208; 3,321,510; 3,488,298; 3,907,868; 4,163,860; 4,578,502; and 5,051,528. PET scrap can be reacted with ethylene glycol, i.e. "glycolysis", to produce bis-(2-hydroxyethyl) terephthalate (BHET), a PET monomer. For example, see U.S. Patent No. 4,078,143, column 1. PET scrap can be melted and reformed without depolymerization. Additionally, there are known methods by which catalyst can be removed from PET production waste. For example, see U.S. Pat. Nos. 4,013,519 and 4,118,582.
Two problems arise with the recycling of scrap PET and PET production waste: the effective separation of ethylene glycol (EG) and DMT, and the removal of the polycondensation catalysts. Separation of EG from DMT prior to DMT purification is important because EG and DMT react to form BHET. Removal of the catalyst is important because it is an unwanted contaminant in DMT.
Accordingly, there is a need for a process in which the ethylene glycol and catalyst can be efficiently removed from DMT in a recovery process.